This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A public health concern exists regarding the prevalence of adverse pregnancy outcomes in the United States. For example, approximately 10% of births are of low weight and 11% of birth outcomes end with a preterm gestational period of less than 37 weeks (i.e., preterm delivery;NCHS, 1998). Because low birth weight and preterm birth are associated with negative health consequences, reducing their prevalence is part of the Healthy People 2010 objectives. Research, however, examining the effect of physical activity on birth outcomes is equivocal (Leiferman &Evenson, 2003). One potential reason for the discrepant results is the lack of consistency in physical activity assessments. The research examining physical activity and adverse pregnancy outcomes is limited, and the existing studies have relied on mostly nonstandardized self-report measures. Few, if any, studies have examined this relationship with objective monitoring devices. Examining whether physical activity may reduce the likelihood of adverse pregnancy outcomes is important because it could provide a cost-effective and modifiable way to reduce this risk (Leiferman &Evenson, 2003). However, before research can effectively examine the role of physical activity in reducing poor birth outcomes - more research is warranted examining the validity and reliability of physical activity measures during pregnancy. Specific Aim #1. We will examine the convergent validity (correlation between measures of the same construct) of objective monitoring (accelerometer, pedometer) and self-report instruments assessed during pregnancy. Based on previous research (Freedson &Miller, 2000;Stein et al., 2003) it is hypothesized that the accelerometer will generate the highest validity coefficients compared to the other exercise measures. Specific Aim #2. We will examine the association between the physical activity assessments taken during pregnancy and low birth weight and preterm delivery. Based on the conclusions of previous researchers (e.g., Campbell &Mottola, 2001;Hatch et al., 1998), it is hypothesized that physical activity will be associated with low birth weight and preterm delivery.